Imaging optical system, projection-type display apparatus, and imaging apparatus

ABSTRACT

The imaging optical system consists of a first optical system and a second optical system in order from a magnified side. The first optical system consists of a la lens group, first optical path bender, and a 1b lens group in order from the magnified side, and the second optical system consists of a 2a lens group, second optical path bender, and a 2b lens group in order from the magnified side. The second optical system forms an image on an image display surface as an intermediate image, and the first optical system forms the intermediate image on a magnified-side conjugate plane, to satisfy the following predetermined Conditional Expression (1),
 
3&lt; d/I   (1).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-104119 filed on May 25, 2016. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an imaging optical system suitable for being used in a projection-type display apparatus having a light valve such as, particularly, a liquid crystal display device or a Digital Micromirror Device (DMD: Registered Trademark) mounted therein, a projection-type display apparatus including this imaging optical system, and an imaging apparatus including this imaging optical system.

2. Description of the Related Art

In recent years, projection-type display apparatuses (also called projectors) having a light valve such as a liquid crystal display device or a Digital Micromirror Device (DMD: Registered Trademark) mounted therein have been in widespread use and have increased in performance. Particularly, with an improvement in the resolution of the light valve, a high demand for the resolution performance of an imaging optical system has also been made.

In addition, in consideration of improving the degree of freedom of the setting of distance to a screen or installability in an indoor space, there has also been a strong demand for mounting an imaging optical system having high versatility, in which higher performance and a wider angle are achieved with a compact configuration, in a projection-type display apparatus.

In order to respond to such a demand, an imaging optical system is proposed in which an intermediate image is formed in a first optical system consisting of a plurality of lenses, and the image is re-formed likewise in a second optical system consisting of a plurality of lenses (see WO09/107553A and JP2006-330410A).

In an imaging optical system constituted by only an optical system having no normal intermediate image formed thereon, in a case where an attempt is made to widen an angle by reducing a focal length, lenses on the magnified side become excessively large in any way. However, in the imaging optical system of an intermediate imaging type as described above, it is possible to shorten the back focus of the second optical system, and to reduce the lens diameters of the second optical system on the magnified side. Therefore, the system is also suitable for widening an angle by reducing a focal length.

However, since the second optical system is a fisheye lens, and distortion greatly remains on a final image plane, WO09/107553A is not suitable as a normal imaging optical system. In addition, since aberration corrections are independently performed in the first optical system and the second optical system using an intermediate image as a boundary, JP2006-330410A does not attain to a wide angle of a level required in these days. Further, in both WO09/107553A and JP2006-330410A, since the intermediate image is formed one time, the entire lens length increases in any way.

SUMMARY OF THE INVENTION

The present invention is contrived in view of such circumstances, and an object thereof is to provide an imaging optical system having high projection performance in which a wide angle is formed and various aberrations are satisfactorily corrected, while achieving a reduction in size in an imaging optical system having an intermediate image formed therein, a projection-type display apparatus including this imaging optical system, and an imaging apparatus including this imaging optical system.

According to the present invention, there is provided an imaging optical system capable of projecting an image, displayed on an image display device disposed on a reduced-side conjugate plane, as a magnified image on a magnified-side conjugate plane, the system comprising, in order from a magnified side: a first optical system which is constituted by a plurality of lenses; and a second optical system which is constituted by a plurality of lenses, wherein the first optical system consists of a 1a lens group, first optical path bending means for bending an optical path on a reflecting surface, and a 1b lens group, in order from the magnified side, the second optical system consists of a 2a lens group, second optical path bending means for bending an optical path on a reflecting surface, and a 2b lens group, in order from magnified side, the second optical system forms the image on the image display device as an intermediate image, the first optical system forms the intermediate image on the magnified-side conjugate plane, and the following Conditional Expression (1) is satisfied, 3<d/I  (1)

where d is a distance on an optical axis from a surface of the 2a lens group on a most reduced side to a surface of the 2b lens group on a most magnified side, and

I is a maximum image height on the reduced side.

In the imaging optical system of the present invention, it is preferable to satisfy the following Conditional Expression (1-1), 5<d/I<15  (1-1).

In addition, it is preferable to satisfy the following Conditional Expression (2), and more preferable to satisfy the following Conditional Expression (2-1), 4<b/a<10  (2) 5<b/a<8  (2-1)

where b is a light flux diameter of a maximum image height in a meridian direction at an F-Number five times a design F-Number, and

a is an on-axis light flux diameter at an F-Number five times the design F-Number.

Meanwhile, the light flux diameters of a and b are set to light flux diameters on the magnified side rather than the lens surface on the most magnified side when a projection distance is set to be infinite. In addition, the position of a diaphragm for determining the F-Number when a and b are calculated is set to a position at which a principal ray of light and an optical axis intersect each other within the second optical system. In addition, the light flux diameter of b is set to a light flux diameter in a direction perpendicular to the principal ray of light.

In addition, it is preferable that the 2a lens group has a positive refractive power.

In addition, it is preferable to satisfy the following Conditional Expression (3), and more preferable to satisfy the following Conditional Expression (3-1), 1<f1/|f|<2.5  (3) 1.3<f1/|f|<2  (3-1)

where f1 is a focal length of the first optical system, and

f is a focal length of the whole system.

In addition, it is preferable to satisfy the following Conditional Expression (4), and more preferable to satisfy the following Conditional Expression (4-1), 5<f2a/|f|<60  (4) 10<f2a/|f|<40  (4-1)

where f2a is a focal length of the 2a lens group, and

f is a focal length of the whole system.

In addition, it is preferable to satisfy the following Conditional Expressions (5) and (6), 1<La/Lc<3  (5) 1.2<Lb/Lc<4  (6)

where La is a distance on the optical axis from a surface of the 2b lens group on the most reduced side to the second optical path bending means,

Lb is a distance on the optical axis from the second optical path bending means to the first optical path bending means, and

Lc is a distance on the optical axis from the first optical path bending means to a surface of the 1a lens group on the most magnified side.

According to the present invention, there is provided a projection-type display apparatus comprising: a light source; a light valve on which light from the light source is incident; and the imaging optical system of the prevent invention as an imaging optical system that projects an optical image of light optically modulated by the light valve onto a screen.

According to the present invention, there is provided an imaging apparatus comprising the imaging optical system of the present invention.

Meanwhile, the term “magnified side” means a projected side (screen side), and the screen side is assumed to be referred to as the magnified side, for the sake of convenience, even in a case of reduction projection. On the other hand, the term “reduced side” means an image display device side (light valve side), and the light valve side is assumed to be referred to as the reduced side, for the sake of convenience, even in a case of reduction projection.

In addition, the term “consist of” is intended to be allowed to include lenses having substantially no power, optical elements, such as a mirror, a diaphragm, a mask, cover glass, or a filter having no power, other than a lens, and the like, in addition to the things enumerated as components.

In addition, the term “lens group” is not necessarily constituted by a plurality of lenses, but may be constituted by only one lens.

In addition, the surface shape of the lens and the sign of the refractive power thereof are assumed to be those in a paraxial region in a case where an aspherical surface is included.

According to the present invention, there is provided an imaging optical system capable of projecting an image, displayed on an image display device disposed on a reduced-side conjugate plane, as a magnified image on a magnified-side conjugate plane, the system comprising, in order from a magnified side: a first optical system which is constituted by a plurality of lenses; and a second optical system which is constituted by a plurality of lenses, wherein the first optical system consists of a 1a lens group, first optical path bending means for bending an optical path on a reflecting surface, and a 1b lens group, in order from the magnified side, the second optical system consists of a 2a lens group, second optical path bending means for bending an optical path on a reflecting surface, and a 2b lens group, in order from magnified side, the second optical system forms the image on the image display device as an intermediate image, the first optical system forms the intermediate image on the magnified-side conjugate plane, and the following Conditional Expression (1) is satisfied, 3<d/I  (1). Therefore, it is possible to form an imaging optical system having high projection performance in which a wide angle is formed and various aberrations are satisfactorily corrected, while achieving a reduction in size.

Since the projection-type display apparatus of the present invention includes the imaging optical system of the present invention, it is possible to project a high-quality image with a wide angle of view, and to reduce the size of the apparatus.

Since the imaging apparatus of the present invention includes the imaging optical system of the present invention, it is possible to acquire a high-quality image with a wide angle of view, and to reduce the size of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a configuration (in common with that of Example 1) of an imaging optical system according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an imaging optical system of Example 2 of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of an imaging optical system of Example 3 of the present invention.

FIG. 4 is a diagram of aberrations of an imaging optical system of Example 1 of the present invention.

FIG. 5 is a diagram of aberrations of an imaging optical system of Example 2 of the present invention.

FIG. 6 is a diagram of aberrations of an imaging optical system of Example 3 of the present invention.

FIG. 7 is a schematic configuration diagram of a projection-type display apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a projection-type display apparatus according to another embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a projection-type display apparatus according to still another embodiment of the present invention.

FIG. 10 is a perspective view of a front side of an imaging apparatus according to an embodiment of the present invention.

FIG. 11 is a perspective view of a rear surface side of the imaging apparatus shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating a configuration of an imaging optical system according to an embodiment of the present invention. The configuration example shown in FIG. 1 is in common with a configuration of an imaging optical system of Example 1 described later. In FIG. 1, an image display surface Sim side is a reduced side, a lens L1 a side of a first optical system G1 is a magnified side, and a shown aperture diaphragm St does not necessarily indicate a size or a shape, but indicates a position on an optical axis Z. In addition, in FIG. 1, an on-axis light flux wa and a light flux wb of the maximum angle of view are also shown together.

This imaging optical system is mounted on, for example, a projection-type display apparatus, and can be used in projecting image information displayed on a light valve onto a screen. In FIG. 1, on the assumption of a case of being mounted on the projection-type display apparatus, an optical member PP assumed to be a filter, a prism and the like which are used in a color synthesis portion or an illumination light separation portion, and the image display surface Sim of the light valve located on the surface of the optical member PP on the reduced side are also shown together. In the projection-type display apparatus, a light flux to which image information is given on the image display surface Sim on an image display device is incident on this imaging optical system through the optical member PP, and is projected onto a screen, not shown, by this imaging optical system.

As shown in FIG. 1, the imaging optical system of the present embodiment consists of the first optical system G1 constituted by a plurality of lenses and a second optical system G2 constituted by a plurality of lenses, in order from the magnified side. The first optical system G1 consists of a 1a lens group G1 a, first optical path bending means R1 for bending an optical path on a reflecting surface, and a 1b lens group G1 b, in order from the magnified side, and the second optical system G2 consists of a 2a lens group G2 a, second optical path bending means R2 for bending an optical path on a reflecting surface, and a 2b lens group G2 b, in order from the magnified side. The second optical system G2 is configured to form an image on the image display surface Sim as an intermediate image, and the first optical system G1 is configured to form the intermediate image on a magnified-side conjugate plane.

As the first optical path bending means R1 and the second optical path bending means R2, for example, a mirror or a prism can be used.

In an optical system for projection constituted by only an optical system having no normal intermediate image formed thereon, in a case where an attempt is made to widen an angle by reducing a focal length, a lens on the magnified side becomes excessively large in any way. However, in an optical system for projection of a type in which intermediate imaging is performed as in the present embodiment, it is possible to shorten a back focus of the first optical system G1, and to reduce the lens diameters of the first optical system G1 on the magnified side. Therefore, the system is suitable for widening an angle by reducing a focal length.

In addition, the 2a lens group G2 a rather than optical path bending means is disposed in close proximity to the reduced side of the intermediate image, and thus it is possible to efficiently bend a ray of light in the vicinity of a maximum image height.

In addition, it is configured to satisfy the following Conditional Expression (1). The ratio value is not set to be equal to or less than the lower limit of Conditional Expression (1), and thus a distance between the 2a lens group G2 a and the 2b lens group G2 b can be prevented from becoming excessively small. Therefore, it is possible to secure an enough distance to dispose the optical path bending means. Meanwhile, in a case where the following Conditional Expression (1-1) is satisfied, it is possible to make characteristics more satisfactory. The ratio value is not set to be equal to or greater than the upper limit of Conditional Expression (1-1), and thus the distance between the 2a lens group G2 a and the 2b lens group G2 b can be prevented from becoming excessively large, which leads to contribution to a reduction in the size of the entire imaging optical system, 3<d/I  (1), 5<d/I<15  (1-1).

Here, d is a distance on the optical axis from the surface of the 2a lens group on the most reduced side to the surface of the 2b lens group on the most magnified side, and

I is a maximum image height on the reduced side.

In the imaging optical system of the present embodiment, it is preferable to satisfy the following Conditional Expression (2). The ratio value is not set to be equal to or less than the lower limit of Conditional Expression (2), and thus it is possible to secure a peripheral light amount ratio even in a case where a lens is used which has a wide angle of view and in which various aberrations are satisfactorily corrected. The ratio value is not set to be equal to or greater than the upper limit of Conditional Expression (2), and thus it is possible to prevent a lens diameter from increasing. Meanwhile, in a case where the following Conditional Expression (2-1) is satisfied, it is possible to make characteristics more satisfactory, 4<b/a<10  (2) 5<b/a<8  (2-1).

Here, b is a light flux diameter of a maximum image height in a meridian direction at an F-Number five times a design F-Number, and

a is an on-axis light flux diameter at an F-Number five times the design F-Number.

In addition, it is preferable that the 2a lens group G2 a has a positive refractive power. With such a configuration, a light flux directed from the 2a lens group G2 a toward the 2b lens group G2 b can be converged, it is possible to reduce the lens diameters of the 2b lens group G2 b.

In addition, it is preferable to satisfy the following Conditional Expression (3). The ratio value is not set to be equal to or less than the lower limit of Conditional Expression (3), and thus it is possible to prevent the refractive power of the first optical system G1 from becoming excessively high. Therefore, it is easy to correct various aberrations while widening an angle. The ratio value is not set to be equal to or greater than the upper limit of Conditional Expression (3), and thus the focal length of the first optical system G1 can be prevented from becoming excessively large, which leads to contribution to a reduction in the size of the entire imaging optical system. Meanwhile, in a case where the following Conditional Expression (3-1) is satisfied, it is possible to make characteristics more satisfactory, 1<f1/|f|<2.5  (3) 1.3<f1/|f|<2  (3-1).

Here, f1 is a focal length of the first optical system, and

f is a focal length of the whole system.

In addition, it is preferable to satisfy the following Conditional Expression (4). The ratio value is not set to be equal to or less than the lower limit of Conditional Expression (4), and thus it is possible to prevent the refractive power of the 2a lens group G2 a from becoming excessively high. Therefore, it is possible to prevent a ray of light around the lenses from changing drastically, and to prevent astigmatism from increasing. The ratio value is not set to be equal to or greater than the upper limit of Conditional Expression (4), and thus it is possible to prevent the refractive power of the 2a lens group G2 a from becoming excessively low. Therefore, the entire length of the second optical system G2 is prevented from increasing, which leads to contribution to a reduction in the size of the entire imaging optical system. Meanwhile, in a case where the following Conditional Expression (4-1) is satisfied, it is possible to make characteristics more satisfactory, 5<f2a/|f|<60  (4) 10<f2a/|f|<40  (4-1).

Here, f2a is a focal length of the 2a lens group, and

f is a focal length of the whole system.

In addition, it is preferable to satisfy the following Conditional Expressions (5) and (6). The ratio value is not set to be equal to or less than the lower limit of Conditional Expressions (5) and (6), and thus a space inside the imaging optical system bent by two optical path bending means can be prevented from becoming excessively small. Therefore, in a case where only the 2b lens group G2 b is received within the projection-type display apparatus, for example, when being mounted in the apparatus body, it is easy to prevent interference between the imaging optical system and the apparatus body. The ratio value is not set to be equal to or greater than the upper limit of Conditional Expressions (5) and (6), and thus the space inside the imaging optical system bent by two optical path bending means can be prevented from becoming excessively large, which leads to contribution to a reduction in the size of the entire imaging optical system, 1<La/Lc<3  (5) 1.2<Lb/Lc<4  (6).

Here, La is a distance on the optical axis from a surface of the 2b lens group on the most reduced side to the second optical path bending means,

Lb is a distance on the optical axis from the second optical path bending means to the first optical path bending means, and

Lc is a distance on the optical axis from the first optical path bending means to a surface of the 1a lens group on the most magnified side.

Next, numerical value examples of the imaging optical system of the present invention will be described.

First, an imaging optical system of Example 1 will be described. FIG. 1 shows a cross-sectional view illustrating a configuration of the imaging optical system of Example 1. Meanwhile, in FIG. 1 and FIGS. 2 and 3 corresponding to Examples 2 and 3 described later, an image display surface Sim side is a reduced side, a lens L1 a side of a first optical system G1 is a magnified side, and a shown aperture diaphragm St does not necessarily indicate a size or a shape, but indicates a position on the optical axis Z. In addition, in FIGS. 1 to 3, an on-axis light flux wa and a light flux wb of the maximum angle of view are also shown together.

The imaging optical system of Example 1 is constituted by the first optical system G1 and the second optical system G2 in order from the magnified side. The first optical system G1 is constituted by a 1a lens group G1 a consisting of seven lenses of lenses L1 a to L1 g, a first optical path bending means R1, and a 1b lens group Glb consisting of six lenses of lenses L1 h to L1 m, in order from the magnified side. The second optical system G2 is constituted by a 2a lens group G2 a consisting of only a lens L2 a, a second optical path bending means R2, and a 2b lens group G2 b consisting of seven lenses of lenses L2 b to L2 h, in order from the magnified side.

Table 1 shows lens data of the imaging optical system of Example 1, Table 2 shows data relating to specifications, and Table 3 shows data relating to aspherical coefficients. In the following, the meanings of symbols in the tables will be described by taking an example of those in Example 1, but the same is basically true of Examples 2 and 3.

In the lens data of Table 1, the column of a surface number indicates surface numbers sequentially increasing toward the reduced side with the surface of a component on the most magnified side set to a first surface, the column of a radius of curvature indicates radii of curvature of respective surfaces, and the column of a surface spacing indicates distances on the optical axis Z between the respective surfaces and the next surfaces. In addition, the column of n indicates refractive indexes of respective optical elements with respect to a d line (wavelength of 587.6 nm), and the column of v indicates Abbe numbers of the respective optical elements with respect to the d line (wavelength of 587.6 nm). Here, the sign of the radius of curvature is set to be positive in a case where a surface shape is convex on the magnified side, and is set to be negative in a case where a surface shape is convex on the reduced side. The lens data also indicates the aperture diaphragm St and the optical member PP together. In the place of a surface number of a surface equivalent to the aperture diaphragm St, a term of (diaphragm) is written together with the surface number.

The data relating to specifications of Table 2 indicates values of a focal length f′, an F-Number FNo, and the total angle of view 2ω.

Meanwhile, numerical values shown in data relating to basic lens data and specifications are standardized so that the focal length of the whole system is set to −1. In addition, the numerical values of each table are rounded off to predetermined decimal places.

In the lens data of Table 1, mark * is attached to the surface number of an aspherical surface, and the numerical values of a paraxial radius of curvature are indicated as the radius of curvature of the aspherical surface. The data relating to the aspherical coefficients of Table 3 indicates surface numbers of the aspherical surfaces and aspherical coefficients relating to these aspherical surfaces. “E-n” (n is an integer) in the numerical values of the aspherical coefficients of Table 3 means “×10⁻¹¹”. The aspherical coefficients are values of respective coefficients KA and Am (m=3 to up to 19) in an aspherical expression represented by the following expression. Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣAm·h ^(m)

Here, Zd is an aspherical depth (length of a vertical line drawn from a point on an aspherical surface having a height h down to a plane perpendicular to the optical axis with which the vertex of the aspherical surface is in contact),

h is a height (distance from the optical axis),

C is a reciprocal of the paraxial radius of curvature, and

KA and Am are aspherical coefficients (m=3 to up to 19).

TABLE 1 Example 1: Lens data (n and ν are based on the d line) SURFACE RADIUS OF SURFACE NUMBER CURVATURE SPACING n ν  *1 −13.5341 0.7825 1.53158 55.08  *2 46.5630 1.3728  3 13.4671 0.5269 1.80610 40.93  4 6.0932 1.9186  5 16.1014 0.3851 1.90366 31.31  6 4.4519 2.7398  7 −12.7527 0.2932 1.67790 55.34  8 9.1944 0.4059  *9 9.1430 0.7434 1.49100 57.58 *10 6.9267 5.1684  11 −176.0312 1.2710 1.74950 35.33  12 −9.0854 0.0059  13 15.7232 0.7117 1.59270 35.31  14 75.8826 4.4682 First optical path ∞ 4.8880 bending means  15 32.5192 1.3986 1.43700 95.10  16 −9.8742 0.0504  17 20.6540 1.9164 1.58913 61.13  18 −6.9917 0.3150 1.80518 25.46  19 5.9697 3.1861 1.49700 81.61  20 −10.3964 5.8531 *21 −5.0533 0.7825 1.49100 57.58 *22 −3.9618 0.0585  23 13.8742 1.0082 1.80518 25.46  24 72.8413 9.7286  25 −73.1289 1.2988 1.80518 25.46  26 −14.1727 6.0000 Second optical ∞ 12.7107 path bending means  27 85.1526 0.3119 1.80610 33.27  28 15.2489 0.7611  29 −23.1418 0.6989 1.83400 37.16  30 −11.2386 0.2019  31 8.5165 1.3487 1.59282 68.62  32 −74.3352 5.4735  33 ∞ 3.2226 (diaphragm)  34 −5.6173 0.2099 1.76182 26.52  35 5.6674 1.2788 1.49700 81.61  36 −7.6484 0.0060  37 15.3930 0.7900 1.49700 81.61  38 −14.6789 2.7502  39 111.5253 1.1007 1.89286 20.36  40 −9.2637 3.5214  41 ∞ 4.8908 1.51633 64.14  42 ∞ 0.0033

TABLE 2 Example 1: Specifications f′ −1.00 FNo. 2.01 2ω [°] 132.6

TABLE 3 Example 1: Aspherical coefficients SURFACE NUMBER 1 2 9 KA −6.62729602E+00 −1.50000000E+01 1.00000000E+00 A3 4.78040058E−04 1.48344442E−02 0.00000000E+00 A4 2.90392561E−03 −2.11538726E−02 5.86605504E−03 A5 −8.59836663E−04 2.16299369E−02 4.63046233E−04 A6 1.15950954E−04 −1.53953236E−02 −7.40310926E−04 A7 3.01050271E−06 7.66642690E−03 8.91452104E−05 A8 −2.95628805E−06 −2.70972859E−03 1.27278478E−06 A9 1.90720930E−07 6.93607366E−04 0.00000000E+00 A10 3.46843295E−08 −1.30181567E−04 0.00000000E+00 A11 −4.46621896E−09 1.79338303E−05 0.00000000E+00 A12 −1.13222509E−10 −1.79221477E−06 0.00000000E+00 A13 3.71448978E−11 1.26346526E−07 0.00000000E+00 A14 −7.63596306E−13 −5.95293417E−09 0.00000000E+00 A15 −1.08638235E−13 1.68121971E−10 0.00000000E+00 A16 4.63008814E−15 −2.15136085E−12 0.00000000E+00 A17 0.00000000E+00 0.00000000E+00 0.00000000E+00 A18 0.00000000E+00 0.00000000E+00 0.00000000E+00 A19 0.00000000E+00 SURFACE NUMBER 10 21 22 KA 1.00000000E+00 −2.71211803E+00 −2.49254719E−01 A3 0.00000000E+00 1.67694089E−02 −1.92363004E−02 A4 5.93943661E−03 2.16127853E−02 3.06331387E−02 A5 −3.67555194E−04 −3.03592567E−03 −1.20877481E−02 A6 −3.85632484E−04 −9.10107684E−03 2.16831346E−03 A7 1.44490847E−05 7.83388631E−03 7.68536101E−05 A8 7.58669238E−06 −2.82875871E−03 2.76727229E−05 A9 0.00000000E+00 4.19914103E−04 −5.59898863E−05 A10 0.00000000E+00 2.18734134E−05 9.03971139E−06 A11 0.00000000E+00 −1.20602669E−05 1.50077521E−06 A12 0.00000000E+00 −1.01279594E−06 −2.55049769E−07 A13 0.00000000E+00 7.77098492E−07 −6.54162721E−08 A14 0.00000000E+00 −1.18559877E−07 5.06837466E−09 A15 0.00000000E+00 8.19144614E−09 2.34973609E−09 A16 0.00000000E+00 −2.49804410E−10 −2.56837999E−10 A17 0.00000000E+00 A18 0.00000000E+00 A19 0.00000000E+00

FIG. 4 shows a diagram of aberrations of the imaging optical system of Example 1. Meanwhile, FIG. 4 shows an aberration diagram at a projection distance of 177, and shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration, in order from the left side. The diagram of aberrations indicating spherical aberration, astigmatism, and distortion indicates aberrations in which the d line (wavelength of 587.6 nm) is used as a reference wavelength. In the spherical aberration diagram, aberrations relating to the d line (wavelength of 587.6 nm), a C line (wavelength of 656.3 nm), and an F line (wavelength of 486.1 nm) are indicated by a solid line, a long dashed line, and a short dashed line, respectively. In the astigmatism diagram, aberrations in a sagittal direction and a tangential direction are indicated by a solid line and a short dashed line, respectively. In the lateral chromatic aberration diagram, aberrations relating to the C line (wavelength of 656.3 nm) and the F line (wavelength of 486.1 nm) are indicated by a long dashed line and a short dashed line, respectively. FNo. in the spherical aberration diagram means an F-Number, and w in the other aberration diagrams means a half angle of view.

In the description of Example 1, symbols, meanings, and description methods of the respective pieces of data are the same as those in the following examples unless otherwise noted, and thus the repeated description thereof will be omitted below.

Next, an imaging optical system of Example 2 will be described. FIG. 2 shows a cross-sectional view illustrating a configuration of the imaging optical system of Example 2. The imaging optical system of Example 2 has the same lens number configuration as that in Example 1, with the exception of the lens number configuration of a first optical system G1. The first optical system G1 of the imaging optical system of Example 2 is constituted by consisting of eight lenses of lenses L1 a to L1 h, a 1a lens group G1 a, first optical path bending means R1, and a 1b lens group Glb consisting of six lenses of lenses L1 i to L1 n, in order from the magnified side. In addition, Table 4 shows lens data of the imaging optical system of Example 2, Table 5 shows data relating to specifications, Table 6 shows data relating to aspherical coefficients, and FIG. 5 shows a diagram of aberrations.

TABLE 4 Example 2: Lens data (n and ν are based on the d line) SURFACE RADIUS OF SURFACE NUMBER CURVATURE SPACING n ν  *1 −21.4405 0.7820 1.49100 57.58  *2 17.7064 1.3307  3 12.3995 0.5120 1.69680 55.53  4 5.8474 1.8914  5 17.8585 0.3736 1.90366 31.31  6 4.2588 2.7441  7 −9.7681 0.2771 1.62041 60.29  8 8.5571 2.6113  9 −33.3349 0.2961 1.72047 34.71  10 7.1960 1.6544 1.77250 49.60  11 −18.4217 3.4806  12 464.2384 1.1394 1.60342 38.03  13 −10.4453 0.1622  14 14.1446 0.7349 1.65412 39.68  15 75.8432 4.3002 First optical path ∞ 4.8848 bending means  16 21.1025 1.1432 1.49700 81.61  17 −19.9429 0.0585  18 20.3186 1.9942 1.58913 61.13  19 −7.2687 0.3242 1.84666 23.78  20 6.2264 3.0602 1.49700 81.61  21 −9.1914 3.8812 *22 −4.8098 0.7820 1.53158 55.08 *23 −3.9102 0.0586  24 26.1899 1.0628 1.80518 25.46  25 −42.5810 9.5914  26 −39.1017 1.4214 1.80518 25.46  27 −12.5575 5.4989 Second optical ∞ 15.3683 path bending means  28 74.8075 0.3183 1.80610 33.27  29 14.4744 0.8662  30 −20.4166 0.6343 1.83400 37.16  31 −10.9626 0.5978  32 8.8399 1.4285 1.59282 68.62  33 −52.3864 5.6031  34 ∞ 3.5130 (diaphragm)  35 −5.3098 0.2160 1.76182 26.52  36 6.3867 1.2171 1.49700 81.61  37 −7.0387 0.0057  38 24.3776 0.7938 1.49700 81.61  39 −11.2764 2.8425  40 356.1866 1.0854 1.89286 20.36  41 −9.0726 3.5191  42 ∞ 4.8877 1.51633 64.14  43 ∞ 0.0037

TABLE 5 Example 2: Specifications f′ −1.00 FNo. 2.01 2ω [°] 132.6

TABLE 6 Example 2: Aspherical coefficients SURFACE NUMBER 1 2 22 KA −3.62865906E+00 −1.44702801E+01 −3.70989034E+00 A3 −1.31434131E−03 1.39603127E−02 −1.95341290E−02 A4 3.13029606E−03 −2.12309352E−02 2.18564697E−02 A5 −8.60084840E−04 2.16852752E−02 −3.09485795E−03 A6 1.14981254E−04 −1.54446658E−02 −9.23843964E−03 A7 3.01391764E−06 7.69599637E−03 7.86708986E−03 A8 −2.96308278E−06 −2.72191549E−03 −2.84042980E−03 A9 1.91694185E−07 6.97174741E−04 4.23047287E−04 A10 3.48603403E−08 −1.30935010E−04 2.19287055E−05 A11 −4.49381221E−09 1.80491937E−05 −1.21477084E−05 A12 −1.14009677E−10 −1.80490076E−06 −1.02013594E−06 A13 3.74325909E−11 1.27322449E−07 7.83083287E−07 A14 −7.69902407E−13 −6.00276672E−09 −1.19550733E−07 A15 −1.09734529E−13 1.69638103E−10 8.26620344E−09 A16 4.68160462E−15 −2.17213913E−12 −2.51445531E−10 A17 0.00000000E+00 0.00000000E+00 A18 0.00000000E+00 0.00000000E+00 SURFACE NUMBER 23 KA −2.30676889E+00 A3 −2.11971082E−02 A4 2.77007396E−02 A5 −1.20307077E−02 A6 2.26736247E−03 A7 6.46348628E−05 A8 2.31858087E−05 A9 −5.63516243E−05 A10 9.14837295E−06 A11 1.62258593E−06 A12 −2.73924227E−07 A13 −6.59117382E−08 A14 5.10996258E−09 A15 2.37086884E−09 A16 −2.59368226E−10 A17 A18

Next, an imaging optical system of Example 3 will be described. FIG. 3 shows a cross-sectional view illustrating a configuration of the imaging optical system of Example 3. The imaging optical system of Example 3 has the same lens number configuration as that in Example 1, with the exception of the lens number configuration of a first optical system G1. The first optical system G1 of the imaging optical system of Example 3 is constituted by a 1a lens group G1 a consisting of five lenses of lenses L1 a to L1 e, a first optical path bending means R1, and a 1b lens group Glb consisting of eight lenses of lenses L1 f to L1 m, in order from the magnified side. In addition, Table 7 shows lens data of the imaging optical system of Example 3, Table 8 data relating to specifications, Table 9 shows data relating to aspherical coefficients, and FIG. 6 shows a diagram of aberrations.

TABLE 7 Example 3: Lens data (n and ν are based on the d line) SURFACE RADIUS OF SURFACE NUMBER CURVATURE SPACING n ν  *1 −13.0518 0.7831 1.53158 55.08  *2 53.4324 1.1069  3 12.6834 0.5338 1.80610 40.93  4 6.2958 1.7177  5 12.6433 0.3952 1.90366 31.31  6 4.6057 2.7478  7 −14.5435 0.2952 1.67790 55.34  8 6.9377 0.4782  *9 10.8264 0.7440 1.49100 57.58 *10 7.9159 4.5881 First optical path ∞ 3.3273 bending means  11 −59.8190 0.8796 1.74950 35.33  12 −11.3463 0.0059  13 14.6852 0.8649 1.59270 35.31  14 3713.1129 8.2657  15 12.1496 1.8251 1.43700 95.10  16 −13.3582 0.0057  17 21.0529 1.8939 1.58913 61.13  18 −7.6748 0.3216 1.80518 25.46  19 4.9616 3.2363 1.49700 81.61  20 −14.2869 5.4530 *21 −5.1198 0.7831 1.49100 57.58 *22 −3.9989 0.0588  23 16.5109 0.9123 1.80518 25.46  24 −438.7278 9.1534  25 −42.0849 1.3042 1.80518 25.46  26 −12.0276 4.9968 Second optical ∞ 12.9842 path bending means  27 69.1180 0.3194 1.80610 33.27  28 14.8391 0.8354  29 −21.7078 0.6251 1.83400 37.16  30 −11.2383 0.0061  31 8.9655 1.4198 1.59282 68.62  32 −48.8451 5.8986  33 ∞ 3.2114 (diaphragm)  34 −5.8492 0.2107 1.76182 26.52  35 5.6919 1.2740 1.49700 81.61  36 −7.2868 0.0060  37 16.8975 0.7524 1.49700 81.61  38 −15.1218 2.9368  39 348.0084 1.0801 1.89286 20.36  40 −8.9629 3.5240  41 ∞ 4.8944 1.51633 64.14  42 ∞ 0.0035

TABLE 8 Example 3: Specifications f′ −1.00 FNo. 2.02 2ω [°] 132.8

TABLE 9 Example 3: Aspherical coefficients SURFACE NUMBER 1 2 9 KA −4.39711147E+00 −1.50000000E+01 1.00000000E+00 A3 9.16864511E−04 1.48771351E−02 0.00000000E+00 A4 2.89267772E−03 −2.11071797E−02 6.00058789E−03 A5 −8.57307839E−04 2.15663281E−02 5.30088598E−04 A6 1.15264488E−04 −1.53387516E−02 −7.24081696E−04 A7 2.99723532E−06 7.63263410E−03 9.19747598E−05 A8 −2.93892374E−06 −2.69579949E−03 −2.33271162E−07 A9 1.89600851E−07 6.89533898E−04 0.00000000E+00 A10 3.44500426E−08 −1.29321776E−04 0.00000000E+00 A11 −4.43360970E−09 1.78022732E−05 0.00000000E+00 A12 −1.12309223E−10 −1.77775823E−06 0.00000000E+00 A13 3.68181577E−11 1.25235136E−07 0.00000000E+00 A14 −7.56322370E−13 −5.89622716E−09 0.00000000E+00 A15 −1.07547454E−13 1.66397900E−10 0.00000000E+00 A16 4.58085614E−15 −2.12773172E−12 0.00000000E+00 A17 0.00000000E+00 0.00000000E+00 0.00000000E+00 A18 0.00000000E+00 0.00000000E+00 0.00000000E+00 A19 0.00000000E+00 SURFACE NUMBER 10 21 22 KA 1.00000000E+00 −2.43915809E+00 −1.10913100E+00 A3 0.00000000E+00 −1.47987340E−02 −1.73680892E−02 A4 5.92633033E−03 2.15652811E−02 3.01885404E−02 A5 −2.49331153E−04 −2.98423037E−03 −1.20836426E−02 A6 −3.74512253E−04 −9.12331226E−03 2.15123108E−03 A7 1.37538719E−05 7.79897004E−03 7.55845488E−05 A8 6.96954755E−06 −2.81417434E−03 2.64939899E−05 A9 0.00000000E+00 4.17091589E−04 −5.56610656E−05 A10 0.00000000E+00 2.17570413E−05 8.93878830E−06 A11 0.00000000E+00 −1.19418230E−05 1.49549569E−06 A12 0.00000000E+00 −1.00462643E−06 −2.48401890E−07 A13 0.00000000E+00 7.70262851E−07 −6.48408467E−08 A14 0.00000000E+00 −1.17430488E−07 5.02009387E−09 A15 0.00000000E+00 8.10744381E−09 2.32563982E−09 A16 0.00000000E+00 −2.47060724E−10 −2.54017060E−10 A17 0.00000000E+00 A18 0.00000000E+00 A19 0.00000000E+00

Table 10 shows values corresponding to Conditional Expressions (1) to (6) of the imaging optical systems of Examples 1 to 3. Meanwhile, the d line is used as a reference wavelength in all the examples, and values shown in the following Table 10 are equivalent to those at this reference wavelength.

TABLE 10 EXPRESSION CONDITIONAL EXAM- EXAM- EXAM- NUMBER EXPRESSION PLE 1 PLE 2 PLE 3 (1) d/I 8.21 9.16 7.88 (2) b/a 6.44 6.25 6.17 (3) f1/|f| 1.74 1.85 1.63 (4) f2a/|f| 21.62 22.44 20.52 (5) La/Lc 1.48 1.55 2.36 (6) Lb/Lc 1.75 1.51 3.23

From the above-mentioned data, it can be understood that the imaging optical systems of Examples 1 to 3 all satisfy Conditional Expressions (1) to (6), and are imaging optical systems having high projection performance which are configured such that the total angle of view is equal to or greater than 120° to have a wide angle and that various aberrations are satisfactorily corrected, while achieving a reduction in size.

Next, a projection-type display apparatus according to an embodiment of the present invention will be described. FIG. 7 is a schematic configuration diagram of a projection-type display apparatus according to the embodiment of the present invention. A projection-type display apparatus 100 shown in FIG. 7 includes an imaging optical system 10 according to an embodiment of the present invention, a light source 15, transmission-type display devices 11 a to 11 c as light valves corresponding to respective beams of colored light, dichroic mirrors 12 and 13 for color decomposition, a cross dichroic prism 14 for color synthesis, capacitor lenses 16 a to 16 c, and total reflection mirrors 18 a to 18 c for deflecting an optical path. Meanwhile, in FIG. 7, the imaging optical system 10 is schematically shown. In addition, an integrator is disposed between the light source 15 and the dichroic mirror 12, but is not shown in FIG. 7.

White light from the light source 15 is decomposed into three colored light fluxes (G light, B light, and R light) by the dichroic mirrors 12 and 13. The decomposed light fluxes are then incident on the transmission-type display devices 11 a to 11 c corresponding to the respective colored light fluxes through the capacitor lenses 16 a to 16 c, respectively, and are optically modulated. The modulated light fluxes are color-synthesized by the cross dichroic prism 14, and then are incident on the imaging optical system 10. The imaging optical system 10 projects an optical image of light optically modulated by the transmission-type display devices 11 a to 11 c onto a screen 105.

FIG. 8 is a schematic configuration diagram of a projection-type display apparatus according to another embodiment of the present invention. A projection-type display apparatus 200 shown in FIG. 8 includes an imaging optical system 210 according to the embodiment of the present invention, a light source 215, DMDs 21 a to 21 c as light valves corresponding to respective beams of colored light, total internal reflection (TIR) prisms 24 a to 24 c for color decomposition and color synthesis, and a polarization separation prism 25 that separates illumination light and projected light. Meanwhile, in FIG. 8, the imaging optical system 210 is schematically shown. In addition, an integrator is disposed between the light source 215 and the polarization separation prism 25, but is not shown in FIG. 8.

White light from the light source 215 is reflected from a reflecting surface inside the polarization separation prism 25, and then is decomposed into three colored light fluxes (G light, B light, and R light) by the TIR prisms 24 a to 24 c. The respective colored light fluxes after the decomposition are incident on the DMDs 21 a to 21 c corresponding thereto and are optically modulated. The modulated light fluxes travel through the TIR prisms 24 a to 24 c again in an opposite direction and are color-synthesized. The synthesized light passes through the polarization separation prism 25 and is incident on the imaging optical system 210. The imaging optical system 210 projects an optical image of light optically modulated by the DMDs 21 a to 21 c onto a screen 205.

FIG. 9 is a schematic configuration diagram of a projection-type display apparatus according to still another embodiment of the present invention. A projection-type display apparatus 300 shown in FIG. 9 includes an imaging optical system 310 according to the embodiment of the present invention, a light source 315, reflection-type display devices 31 a to 31 c as light valves corresponding to respective beams of colored light, dichroic mirrors 32 and 33 for color separation, a cross dichroic prism 34 for color synthesis, a total reflection mirror 38 for optical path deflection, and polarization separation prisms 35 a to 35 c. Meanwhile, in FIG. 9, the imaging optical system 310 is schematically shown. In addition, an integrator is disposed between the light source 315 and the dichroic mirror 32, but is not shown in FIG. 9.

White light from light source 315 is decomposed into three colored light fluxes (G light, B light, and R light) by the dichroic mirrors 32 and 33. The respective colored light fluxes after the decomposition are incident on the reflection-type display devices 31 a to 31 c corresponding to the respective colored light fluxes through the polarization separation prisms 35 a to 35 c, respectively, and are optically modulated. The modulated light fluxes are color-synthesized by the cross dichroic prism 34, and then are incident on the imaging optical system 310. The imaging optical system 310 projects an optical image of light optically modulated by the reflection-type display devices 31 a to 31 c onto a screen 305.

FIGS. 10 and 11 are appearance diagrams of a camera 400 which is an imaging apparatus of an embodiment of the present invention. FIG. 10 shows a perspective view when the camera 400 is seen from the front side, and FIG. 11 is a perspective view when the camera 400 seen from the rear surface side. The camera 400 is a single-lens digital camera, having no reflex finder, which has an interchangeable lens 48 detachably mounted therein. The interchangeable lens 48 has an imaging optical system 49 which is an optical system according to the embodiment of the present invention housed within a lens barrel.

This camera 400 includes a camera body 41, and is provided with a shutter button 42 and a power button 43 on the upper surface of the camera body 41. In addition, operating portions 44 and 45 and a display portion 46 are provided on the rear surface of the camera body 41. The display portion 46 is used for displaying a captured image or an image within an angle of view before image capture.

An imaging aperture on which light from an imaging target is incident is provided on the front central portion of the camera body 41, a mount 47 is provided at a position corresponding to the imaging aperture, and the interchangeable lens 48 is mounted onto the camera body 41 through the mount 47.

The camera body 41 is provided therein with an imaging device (not shown) such as a charge coupled device (CCD) that outputs an imaging signal according to a subject image formed by the interchangeable lens 48, a signal processing circuit that processes the imaging signal which is output from the imaging device to generate an image, a recording medium for recording the generated image, and the like. In this camera 400, a still image or a moving image can be captured by pressing the shutter button 42, and image data obtained by this image capture is recorded in the recording medium.

Hereinbefore, the present invention has been described through embodiments and examples, but the imaging optical systems of the present invention are not limited to those of the above examples, and can be variously modified. For example, it is possible to appropriately change the radius of curvature, the surface spacing, the refractive index, and the Abbe number of each lens.

In addition, the projection-type display apparatuses of the present invention are also not limited to the above configurations. For example, the light valves which are used and the optical members which are used for light flux separation or light flux synthesis are not limited to the above configurations, and can be modified in various forms.

In addition, the imaging apparatus of the present invention is also not limited to the above configuration, and can also be applied to, for example, a single-lens reflex camera, a film camera, a video camera, and the like.

EXPLANATION OF REFERENCES

-   -   10, 210, 310: imaging optical system     -   11 a to 11 c: transmission-type display device     -   12, 13, 32, 33: dichroic mirror     -   14, 34: cross dichroic prism     -   15, 215, 315: light source     -   16 a to 16 c: capacitor lens     -   18 a to 18 c, 38: total reflection mirror     -   21 a to 21 c: DMD     -   24 a to 24 c: TIR prism     -   25, 35 a to 35 c: polarization separation prism     -   31 a to 31 c: reflection-type display device     -   41: camera body     -   42: shutter button     -   43: power button     -   44, 45: operating portion     -   46: display portion     -   47: mount     -   48: interchangeable lens     -   49: imaging optical system     -   100, 200, 300: projection-type display apparatus     -   105, 205, 305: screen     -   400: camera     -   G1: first optical system     -   G1 a: 1a lens group     -   Glb: 1b lens group     -   G2: second optical system     -   G2 a: 2a lens group     -   G2 b: 2b lens group     -   L1 a to L2 h: lens     -   PP: optical member     -   R1: first optical path bending means     -   R2: second optical path bending means     -   Sim: image display surface     -   St: aperture diaphragm     -   wa: on-axis light flux     -   wb: light flux of maximum angle of view     -   Z: optical axis 

What is claimed is:
 1. An imaging optical system capable of projecting an image, displayed on an image display device disposed on a reduced-side conjugate plane, as a magnified image on a magnified-side conjugate plane, the system comprising, in order from a magnified side: a first optical system which is constituted by a plurality of lenses; and a second optical system which is constituted by a plurality of lenses, wherein the first optical system consists of a 1a lens group, first optical path bending means for bending an optical path on a reflecting surface, and a 1b lens group, in order from the magnified side, the second optical system consists of a 2a lens group, second optical path bending means for bending the optical path on a reflecting surface, and a 2b lens group, in order from magnified side, the second optical system forms the image on the image display device as an intermediate image, the first optical system forms the intermediate image on the magnified-side conjugate plane, the following Conditional Expression (1) is satisfied, 3<d/I<15  (1) where d is a distance on an optical axis from a surface of the 2a lens group on a most reduced side to a surface of the 2b lens group on a most magnified side, and I is an image height on the reduced side conjugate plane, and the following Conditional Expression (4) is satisfied, 5<f2a/|f|<60  (4) where f2a is a focal length of the 2a lens group, and f is a focal length of the system.
 2. The imaging optical system according to claim 1, wherein the 2a lens group has a positive refractive power.
 3. The imaging optical system according to claim 1, wherein the following Conditional Expression (3) is satisfied, 1<f1/|f|<2.5  (3) where f1 is a focal length of the first optical system.
 4. The imaging optical system according to claim 3, wherein the following Conditional Expression (3-1) is satisfied, 1.3<f1/|f|<2  (3-1).
 5. The imaging optical system according to claim 1, wherein the following Conditional Expressions (5) and (6) are satisfied, 1<La/Lc<3  (5) 1.2<Lb/Lc<4  (6) where La is a distance on the optical axis from a surface of the 2b lens group on the most reduced side to the second optical path bending means, Lb is a distance on the optical axis from the second optical path bending means to the first optical path bending means, and Lc is a distance on the optical axis from the first optical path bending means to a surface of the 1a lens group on the most magnified side.
 6. The imaging optical system according to claim 1, wherein the following Conditional Expression (1-1) is satisfied, 5<d/I<15  (1-1).
 7. The imaging optical system according to claim 1, wherein the following Conditional Expression (4-1) is satisfied, 10<f2a/|f|<40  (4-1).
 8. A projection-type display apparatus comprising: a light source; a light valve on which light from the light source is incident; and the imaging optical system according to claim 1 as an imaging optical system that projects the light optically modulated by the light valve, the light valve being the image display device, onto a screen as the image.
 9. An imaging apparatus comprising the imaging optical system according to claim
 1. 